If authorized, you can identify the volume to the CVAFDIR, CVAFDSM, CVAFFILT, and CVAFSEQ macros by specifying the address of the UCB. These macros do not accept the address of a UCB copy. If your program is not authorized, specify the address of a SAM or EXCP DEB opened to the volume's VTOC.

The data extent block (DEB) can be obtained by opening a DCB for INPUT, using the RDJFCB and OPEN TYPE=J macros. (After issuing an OPEN TYPE=J macro, the DCB's DCBDEBA field contains the DEB's address.) The DCB's DDNAME must identify a DD statement allocated to the unit whose VTOC is to be accessed. Once your program issues the RDJFCB macro, it must initialize the JFCBDSNM field with the data set name of the format-4 DSCB: 44 bytes of X'04'. The RDJFCB macro is described under RDJFCB Macro Specification; the OPEN macro is described under OPEN - Initialize Data Control Block for Processing the JFCB. For an extended address volume the DCB macro must point to a DCBE where the EADSCB=OK keyword is specified. If you do not code this option, the OPEN function will issue ABEND 113-48 and message IEC142I.

If a CVAF macro call specifies IOAREA=KEEP, a subsequent CVAF call using a different CVAF parameter list (CVPL) might omit the UCB and DEB keywords and supply the IOAREA address from the other CVPL by using the IOAREA keyword.